In a reflector antenna[?], the relative reduction in the effective aperture of the antenna caused by the masking effect of other antenna parts, such as a feed horn or a secondary reflector, which parts obstruct the radiation path.
... Erläuterungen des Hegelschen Systems (1840)
Vorlesungen über Schelling (1842)
System der Wissenschaft (1850)
Meine Reform der Hegelschen Philosop ...